Site owner appoints moderators, but they can only vote on what to do, not do.

Refer to : by @slrslr
I don't think it's fair to give a privilege to the topic starter to remove any comments attached to his topic.
That will hurt the freedom of speech in the site.

Rather, the site owner can appoint several moderators to deal with spams and vandalism.
Moreover, the moderators can not remove or change anything, but they can only vote on [remove this] on each comment or topic. (Of course it's better if the owner could choose whether they can remove not just vote on [remove]. ) If the number of votes reaches the pre-defined number, then it alarms the owner or removes the alarmed comment or post automatically.